Pressure relief or bypass valves conventionally include an adjustable or non-adjustable spring-loaded valve in which a plug is seated over an internal orifice leading to a pressurized fluid line, such as that used in a paint circulation and/or application system. The spring is used to bias the plug into a seated or closed position when the pressure in the pressurized fluid line is below the resistance exerted by the spring. When the pressure inside the system reaches a level sufficiently high enough to overcome the resistance of the spring, the plug is lifted off of the orifice allowing pressurized fluid to flow past the valve and through the orifice. Unfortunately, the simplicity of this type of system also comes with several inherent deficiencies or issues. Each of these issues manifests itself in one way or another in the pressure relief valves that are currently available.
First, existing pressure relief valves tend to open and shut frequently producing what one skilled-in-the-art will describe as “chatter” or a “water hammer” effect. This phenomenon arises when the valve is forced to rapidly cycle between its open and closed positions. More specifically, if the pressurized fluid line becomes partially constricted or blocked or the pump is adjusted to increase flow, the pressure in the pressurized fluid line will increase. At some point, this increase in pressure in the pressurized fluid line will equal and/or surpass the resistance of the spring in the pressure relief valve. Once the pressure set point has been exceeded (e.g., resistance of the spring is overcome), the seal between the valve plug and the valve seat is broken and the valve opens, thereby permitting flow through the valve. Once a small amount of liquid passes through the orifice and into the valve, the excess pressure in the pressurized fluid line is relieved and the magnitude of the pressure in the line decreases. If the pressure in the pressurized fluid line falls below the pressure set point of the valve, the valve will quickly close. However, if the cause of the initial pressure increase in the fluid line has not been remedied, then the pressure will quickly build up again to a level above the valve's pressure set point and the valve will reopen. This cycling of the valve between open and closed positions can continue to occur over and over again. When this happens, the continual opening and closing of the valve can result in undesirable chatter or water hammer sounds, as well as the occurrence of a significant amount of vibration.
Second, conventional pressure relief valves used in a paint circulation and/or application system are often off-set from the pressurized fluid line or located a short distance from the main fluid flow. This is typically accomplished by connecting the valve to the pressurized fluid line through the use of a pipe or tube that is about 0.5-5.0″ in length. When the valve is closed, fluid is initially forced by the pressure in the pressurized fluid line to flow into the connecting tube. Once this fluid enters the connecting tube, it is no longer subject to the same flow conditions as that established in the main fluid circulating line. Thus the fluid in this connecting tube may over time become stagnant and begin to phase separate (e.g., separation between liquid phases or between solid/liquid phases). Phase separation in the fluid may lead to the agglomeration and sedimentation of any solids present (e.g., pigments, additives, etc.) in the fluid. The presence of sedimentation in the connecting tube may plug the tube, thereby preventing the valve from operating properly or when the valve does operate, the sediment may damage the valve's internal components, thereby requiring the valve to be replaced.
In addition, if any sediment in the connecting tube gets disturbed, it can reenter the pressurized fluid line, flow downstream, and ultimately cause additional issues. For example, agglomerated pigment particles that make their way into the paint applied to a manufactured part are known to one skilled-in-the-art to be a root cause of visible point defects in the final paint finish. The occurrence of such defects will ultimately result in an increased amount of scrap and higher production costs. The conventional method of addressing this issue through the periodic removal and cleaning of the pressure relief valve and connecting tube also leads to higher manufacturing costs and losses in productivity.
Accordingly, there exists a continual need or desire for the development and availability of improved pressure relief valve systems for pumps and pressurized fluid circulation systems that provide pressure relief when the pressure set point is exceeded and that do not chatter, vibrate, or produce a water hammer noise. The desire also exists in the industry that such improved pressure relief valve systems will minimize the occurrence of sedimentation and reduce the need to periodically inspect, remove, and clean the components that comprise the system.